Image decoding method, image coding method, image decoding apparatus, image coding apparatus, and image coding and decoding apparatus

Abstract

An image decoding method of decoding, on a per-block basis, a coded image included in a bitstream, includes: performing arithmetic decoding on a current block to be decoded; determining whether or not the current block is at the end of a slice; determining, when it is determined that the current block is not at the end of the slice, whether or not the current block is at the end of a sub-stream which is a structural unit of the image that is different from the slice; and performing arithmetic decoding on a sub-last bit and performing arithmetic decoding termination, when it is determined that the current block is at the end of the sub-stream.

The invention claimed is: 
     
       1. An image decoding method of decoding, on a per-block basis, a coded image included in a bitstream, the image decoding method comprising:
 a first performing of arithmetic decoding on a current block to be decoded; 
 a second performing of arithmetic decoding on an end-of-slice flag indicating whether or not the current block is at the end of the slice; 
 a first determining of determining whether or not the current block is at an end of a slice according to the arithmetically decoded end-of-slice flag; 
 a third performing of performing arithmetic decoding termination as first termination when the arithmetically decoded end-of-slice indicates a predetermined value of 1; 
 a second determining of determining whether or not the current block is at an end of a sub-stream when it is determined that the current block is not at the end of the slice, the sub-stream being a structural unit of the image that is different from the slice; 
 a fourth performing of arithmetic decoding on a sub-last bit corresponding to a current sub stream, indicating the end of the sub-stream, and being different from the current block, to restore a value of 1 when it is determined that the current block is at the end of the sub-stream; 
 a fifth performing of performing arithmetic decoding termination, as second termination, which is triggered by restoring the value of 1; and 
 searching a beginning of a next sub stream, 
 wherein the second termination is same processing as the first termination, and 
 wherein the first performing, the second performing, the first determining, the second determining, the fourth performing, and the fifth performing are repeatedly performed until the third performing is performed.